Field of the Invention
The present invention concerns a method of installing bundles of optical fibers in a multi-dwelling unit or building to provide network access for a number of premises in the building, and tools for performing the installation.
Discussion of the Known Art
To provide fiber optic network service to subscribers or users who occupy a number of premises inside a multi-dwelling unit (MDU) such as an apartment or office building, bundles or tubes containing optical fibers are typically installed along the walls of hallways or corridors leading to the various premises. One or more fibers are designated for servicing a particular living unit or premises in the MDU. Such fiber bundles are commercially available from, e.g., OFS Fitel, LLC, under the registered trademark EZ-Bend®.
At or near an entrance to each premises, a fiber (or fibers) designated for the premises is removed from the bundle, and an end length of the fiber is retained or stored in an interconnect box or adapter mounted nearby. A drop fiber is routed from inside the premises to the box or adapter where it is connected to the corresponding designated fiber from the bundle, thus allowing users inside the premises to access the network through the drop fiber.
So-called “pullback” solutions are known with respect to solid-walled tubes that contain loose floating fibers that are either tight buffered (e.g., 900 μm OD), or bare. The tubes are installed along a hallway wall, and a designated fiber is accessed by forming two small openings a certain length apart in the tube wall. The designated fiber is identified and pulled slightly out of one opening and cut. The fiber is then pulled completely out of the second opening, causing the cut end of the fiber to be pulled back inside the tube from the first opening as the fiber is pulled out of the second opening. The end length of the fiber is then stored in an interconnect box mounted near the second opening in the tube, for connection to the drop fiber from the premises.
Alternate solutions include the bundling of buffered optical fibers each with an OD of from 900 μm to 3.0 mm, into cables (or “cords”) by the use of a light cable binder (e.g., an aramid or polyester yarn), or by covering the fibers with a polymer outer jacket. The binder or outer jacket is removed at a first location to expose a desired fiber, and the fiber is cut. The installer then moves several feet along the bundle to a second location, and opens the binder or outer jacket holding the fibers together. A designated fiber is pulled out of the bundle at the second location, and the cut end length of the fiber is stored for connection with a drop fiber.
An MDU fiber installation solution offered by 3M™ Company under the name “One Pass Pathways” includes a PVC duct or tube containing multiple fibers, wherein the duct has an adhesive backing. To install the duct along a wall, the adhesive backing is exposed by peeling off a protective strip from the backing on the duct as the duct is being unwound from a reel and applied to the wall.
The known methods of installing bundles or tubes of optical fibers along hallways in MDUs usually require large and expensive moldings to be placed over the installed bundles to keep them hidden from view. Otherwise, the bundles can present an unsightly appearance. Another problem stems from the fact that most hallway walls are not flat or smooth over their entire length, e.g., building supports and other structural or decorative objects often cause the wall to protrude at various locations, thus requiring the fiber bundles to conform with sharp corners or bends over their installation span. Even if the bundle contains bend insensitive fibers, an outside jacket or cover on the bundle may be unable to lie flush against the wall at such locations without damage.
So-called blown fiber optic cables having a low friction outer jacket are offered by AFL Telecommunications under the registered mark MicroCore®. According to the company, a 12-fiber version of the cable has an OD of only 1.6 mm, but the minimum allowable bend radius for the cable is 32 mm.
A high density and flexible optical fiber cable is available from OFS Fitel, LLC, under the registered trademark Accu Pack®. See U.S. Pat. No. 7,720,338 (May 18, 2010) which is incorporated by reference. Up to twelve color coded, 250 micron bend-insensitive optical fibers are contained in a round dual layer buffer encasement having an OD of only about 1.4 mm, and an allowable bend radius as small as 5 mm. As sold, Accu Pack cables also have a round outer jacket with an OD of about 4.8 mm, and a yarn reinforcement layer between the jacket and the encased fibers.
Tools capable of opening an optical fiber cable in the form of a flat ribbon of parallel fibers and a surrounding sheath are also known. See, e.g., U.S. Pat. No. 6,909,832 (Jun. 21, 2005). The tools are not constructed for opening a flat ribbon cable midspan to gain access to the sheathed fibers, however. The mentioned “One Pass Pathways” system of 3M does include a so-called “window cut” template (3M prod. # WC-TEMP-20) in the form of an elongated rectangular plate having an axial slot, and an associated cutting tool (# WC-TOOL-50) that resembles a potato “peeler.” According to the 3M procedure, after the PVC duct is installed, it can be entered midspan to access a desired fiber by urging the template lengthwise over the duct until the duct covering protrudes through the slot in the template. The cutting tool is then used to peel away the protruding cover material and expose the fibers for access. Other tools from Miller® (# MSAT 5) and Uraseal® (# ACFO 6278) work to open an uninstalled fiber bundle by aligning the bundle in a guide channel, and then pulling the bundle past a blade in the channel to cut the bundle open and expose the fibers, according to the tool vendors.
Patent Application Pubs. No. US 2012/0020635 (Jan. 26, 2012), No. US 2012/0138214 (Jun. 7, 2012), and No. 2012/0066987, all of which are incorporated by reference, disclose procedures and tools for installing a single fiber inside a premises by applying an adhesive component or substance about the fiber and onto an adjacent supporting surface. The publications are not directed to the installation of a bundle of fibers along a hallway in a MDU wherein the bundle is opened midspan so that a fiber can be removed and retained for connection to a drop fiber from the designated premises, however.
In view of the above, there is a need for a method or procedure including tools that will reduce the time and cost for installing optical fiber bundles along walls or other supporting surfaces in halls or corridors of a MDU, and for accessing a fiber midspan of the bundle so that the fiber can be cut and an end length of the fiber retained near the premises for which the fiber is designated. There is also a need for such a procedure wherein the finished installation can present a more pleasing visual appearance than existing fiber bundle installations.